Hi,
Charts—specifically those with multiple lines—are broken in Xcode 27.
First, I spotted the bug in my program, and then I checked your example.
Your own example Plotting-multiple-lines is not working correctly anymore. It shows 1 line or sometimes no lines at all, depending on the order of the data.
It depends on how the data is passed to the chart. If the data is passed as separate series, it works.
In Visualizing your app’s data it works, but the data is passed as described before.
Don't follow Microslop: have the AI generate the code and then skip the tests.
This is a serious bug that requires a lot of work to rearrange the data, just to work around the issue.
Christian